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Hi everyone,

I'm currently in the middle of rebuilding my 2005 E90 325I N52 with 200,000kms. Everyone has heard of the N52 oil consumption problems (due to wrong piston/ring design) which affected my car aswell, as it consumed oil since the day 1. The last half year oil consumption reached 1 liter/300km, and even 1 liter/150km when accellerating hard. Sparkplugs could be replaced after just 1000km since they where soaking in oil, and the Cathalythic converter didn't like it either.
So i decieded to rebuild the engine.

Since i have some time off now and am waiting for the parts to arrive i thought i might as well take you on a little journey on what to expect when (maybe one day) you open up your engine too.

I decieded to leave the engine in hanging and not to take it out entirely.


The cilinder head out (currently being machined by a proffessional). Unfortunately idn't take a good picture of the valves, but after years of oil consumption i can say they were really cooked with oil. One thing i noticed was that 2 alu bolts snapped were snapped off, namely the 2 head bolts at the front of the engine. More people have reported these bolts to be snapped.


Exhaust ports were full of carbon aswell


Head gasket looked fine


Pistons, with piston 2, 3 and 4 being the worst off:




Piston rings of these 3 pistons were also in bad condition, the oil scrape rings had a lot of carbon deposit on them:



Decieded to go with new pistons, as over the years the piston is redesigned to get rid of the oil consumption problems. A Ebay seller sells these pistons with rings already on them. The pistons and rings are genuine Kolbenschmidt.

New pistons compared to old ones, notice how the oil holes are different:




The project so far cost me around €4000, since i decieded to replace some parts which may go out around 200k, such as: waterpump, thermostat, power steering pump (squeeky sound), v belt and components, clutch (single mass flly wheel upgrade), new lifters, and the entire front wheel suspension. As well as the tools such as a timing kit, valve stem tools etc. Also resurfacing the cilinder head which cost me €600. And not to forget the bolts which are mostly aluminum so one time use...
Now that everything is open, i'm also looking into MILVS, which supposedly increase the valve lift, which makes for more power.

So just a general overview of another rebuilding project